The present invention relates to methods of forming high temperature superconducting Josephson junctions, more particularly, to a method of forming a high temperature superconducting Josephson junction which achieves a formation of a Josephson junction having high characteristics conveniently and quickly without necessitating costly micromachining facilities.
A high temperature superconducting Josephson device has gained a high attention and has been required to be commercialized as a new electronic device which realizes, for example, an ultrahigh frequency generating device capable of generating frequencies in a rang of terahertz or more, an ultrahigh frequency detecting device capable of detecting frequencies in a range of terahertz or more, a SQUID (superconducting quantum interference device) magnetometric sensor and, further, a digital device carrying a mass information processing system.
On the other hand, when the Josephson junction is formed using a single crystal or a thin film, the micromachining facilities which are used for producing a semiconductor device such as a convergence ion beam etching device and a photolithography device has ordinarily been employed. There, however, is a problem in using the micromachining facilities for producing such devices that, for example, not only a tremendously high cost, but also a complexity of production process and an extended period of production time are necessary. Further, it is difficult to conduct a study associated with the Josephson junction at a research institute without having the micromachining facilities whereupon, since the micromachining facilities are extremely highly priced, it is a present situation that a number of researchers who are related with the Josephson junction is limited.
Further, it is considered essential to achieve downsising the Josephson device from a viewpoint of, for example, prevention of malfunction to be caused by heat generation, reduction of power consumption, enhancement of integration and enhancement of characteristics.
The present invention has been accomplished under these circumstances and has an object to provide a method of forming a novel high temperature superconducting Josephson junction which achieves a formation of a Josephson junction having high characteristics conveniently and quickly without necessitating a costly micromachining facilities.
In order to attain the above-described object, the present invention provides, as a first aspect, a method of forming a high temperature superconducting Josephson junction comprising the steps of:
crossing high temperature superconducting whisker crystals with each other;
subjecting the thus crossed high temperature superconducting whisker crystals to thermal treatment, and
forming a Josephson junction in a combined portion of the high temperature superconducting whisker crystals or in a neighborhood of the combined portion.
As a second aspect, the present invention provides a method of forming a high temperature superconducting Josephson junction comprising the steps of:
crossing linear high temperature superconducting thin films mask-processed into an elongate linear shape with each other on a substrate,
subjecting the thus crossed linear high temperature superconducting thin films mask-processed into an elongate linear shape to thermal treatment; and
forming a Josephson junction between the linear high temperature superconducting thin films.
As a third aspect, the present invention provides a method of forming a high temperature superconducting Josephson junction comprising the steps of:
crossing a linear high temperature superconducting thin film mask-processed into an elongate linear shape and a high temperature superconducting whisker crystal;
subjecting the thus crossed linear high temperature superconducting thin film mask-processed into an elongate linear shape and high temperature superconducting whisker crystal to thermal treatment; and
forming a Josephson junction between the linear high temperature superconducting thin film and the high temperature superconducting whisker crystal.
As a fourth aspect, the present invention provides the method of forming the high temperature superconducting Josephson junction of the above-described first aspect in which one or both of the high temperature superconducting whisker crystals are substituted by a linear high temperature superconducting monocrystal processed into an elongate linear shape.
As a fifth aspect, the present invention provides the method of forming the high temperature superconducting Josephson junction of the above-described third aspect in which the high temperature superconducting whisker crystal is substituted by a linear high temperature superconducting monocrystal processed into an elongate linear shape.
As a sixth aspect, the present invention provides the method of forming the high temperature superconducting Josephson junction of any one of the foregoing aspects in which the high temperature superconducting whisker crystal, the linear high temperature superconducting thin film or the linear high temperature superconducting monocrystal which is to form a Josephson junction is a compound containing at least one phase of Bismuth 2212 phase, Bismuth 2201 phase and Bismuth 2223 phase.
As a seventh aspect, the present invention provides the method of forming the high temperature superconducting Josephson junction of any one of the foregoing aspects in which the high temperature superconducting whisker crystal, the linear high temperature superconducting thin film or the linear high temperature superconducting monocrystal which is to form a Josephson junction turns mutual the c-face up, and forming a Josephson junction.
As an eighth aspect, the present invention provides the method of forming the high temperature superconducting Josephson junction of any one of the foregoing aspects in which the high temperature superconducting whisker crystal, the linear high temperature superconducting thin film or the linear high temperature superconducting monocrystal which is to form a Josephson junction are adjusted at 45 to 90 degrees in the cross angle, and forming a Josephson junction.
Further, as a ninth aspect, the present invention provides the method of forming the high temperature superconducting Josephson junction of any one of the foregoing aspects in which the Josephson junction to be formed is an intrinsic Josephson junction.
Furthermore, as a tenth aspect, the present invention also provides a high temperature superconducting Josephson device provided with a Josephson junction to be formed by the method of forming the high temperature superconducting Josephson junction of any one of the foregoing aspects in which the high temperature superconducting Josephson device using other portions than a junction portion of a high temperature superconducting whisker crystal, a linear high temperature superconducting thin film or a linear high temperature superconducting monocrystal imparted with the Josephson junction as a wire material for a wire connection.